Eric Teetsel, executive director of the Manhattan Declaration, echoed Anderson and Walker's remarks in a Wednesday interview with The Christian Post.

"As the 28-year-old executive of the Manhattan Declaration, I join my 20-something colleagues Ryan Anderson and Andrew Walker of the Heritage Foundation in echoing Twain's famous line, 'the reports of my death have been greatly exaggerated.' Both the polling and the voters have demonstrated time and again Americans' strong support for marriage. What future voters may decide obviously remains to be seen; however, beating a retreat because the victory of the anti-marriage movement seems inevitable is a sure-fire way to guarantee precisely that result," Teetsel said.

Will was part of a panel discussion about the U.S. Supreme Court's Friday decision to review two gay marriage cases. The court follows public opinion, Will noted, and the nation has seen a shift in favor of gay marriage. At the same time, Will believes the court may be unlikely to decide the legality of gay marriage for all states because it would remove the debate from democratic deliberative discourse.

"They don't want to do what they did with abortion. The country was having a constructive accommodation on abortion, liberalizing abortion laws. The court yanked the subject out of democratic discourse and embittered the argument," Will said.

Another possible outcome, Will believes, is that the court will more directly address whether gay marriage is a legal right under the U.S. Constitution because, "there is something like an emerging consensus."

Anderson and Walker noted that they were both born in the 1980s and worked to explain "what marriage is and why it matters," as employees of The Heritage Foundation, a conservative think tank.

Anderson co-authored, with Sherif Girgis and Dr. Robert P. George, a recently published book defending traditional marriage called, What is Marriage? Man and Woman: A Defense. Anderson and Walker pointed out that Girgis, a 2008 Rhodes Scholar pursuing advanced degrees at Yale and Princeton, is also young.

Anderson and Walker acknowledged that "there are strong cultural headwinds against marriage," but believe that legalized same-sex marriage is not inevitable. Public opinion is not determined by fate, they write, but "will depend on human choice."

The abortion issue is illustrative, Anderson and Walker believe. They note that after Roe v. Wade, the 1973 U.S. Supreme Court decision that legalized abortion, many were saying some of the same things they say today about gay marriage -- the issue is settled and the future is inevitable. Americans have not become increasingly pro-choice since Roe v. Wade, though, and pro-lifers have scored important victories on measures restricting abortion.

Advocates of maintaining the traditional definition of marriage have a good chance to move public opinion in their direction in the future, Anderson and Walker believe, for two reasons.

First, when young Americans, the strongest advocates of gay marriage, grow up and start their own families, "they'll develop greater appreciation for what makes a marriage and for the gendered nature of parenting."

And second, as more states redefine marriage to include same-sex couples, the negative consequences will become more apparent, similar to how "the harms of divorce and non-marital childbearing led to the marriage movement of the 1980s and '90s."

"The right question is not what will happen, but what we should do," they wrote. "Would George Will give up market economies if polls showed an 'emerging consensus' in favor of socialism? We think not."